More than 80 patients have been diagnosed, most of whom are Ashkenazi Jews. The disease often appears in the first year of life as either delayed motor development or corneal clouding. There are conflicting reports concerning the progressive nature of the disease. Some patients have clear deterioration, while others seem to stay at the same level of the disease for a long time. This study may lead to a better understanding of the disease, the medical difficulties of patients, and better ways of diagnosing ML-IV.